The effect of operative technique and tibial osteotomy ratio on post-surgical complications in dogs with medial patella luxation

Abstract

Background: Medial patellar luxation is a common cause of hindlimb lameness in dogs, affecting both small and large breeds. The condition arises from developmental abnormalities and anatomical irregularities in the hindlimb. Tibial tuberosity transposition is a widely used surgical technique for realigning the quadriceps mechanism and treating MPL. Postoperative complications are common following surgical treatment. During the routine evaluation of post operative radiographs, osteotomy segment size appeared to be associated with an increased incidence of complications. This prompted investigation into this possible association between osteotomy segment size and the incidence of complications.

Hypothesis: The complication rate significantly differs when the osteotomized segment of the tibial tuberosity is transposed medially and measures less than 80% of the mid-tibial diaphysis on preoperative radiographs

Animals: Client-owned dogs (n= 88) that underwent MPL surgery Methods: Records of 88 dogs (108 stifles) that underwent TTT for treatment of MPL were reviewed. Data collected included patient signalment, clinical presentation, surgical factors, pre and postoperative radiographs and complications. The dimensions of tibial tuberosity osteotomy were calculated as a ratio to preselected tibial dimensions based on immediate postoperative radiographs. Mixed-effects logistic regression analysis was performed to determine the impact of osteotomy segment size (O1:D3 ratio) on the occurrence of post-surgical complications following TTT.

Results: Out of 108 surgical procedures performed, 40 (37%) resulted in complications. There was no significant difference in overall complication rates related to patient factors or surgical variables (such as pin direction, tension band, open physis, and complete osteotomy). However, concurrent trochlear augmentation procedures were associated with a decreased risk of complications (hazard ratio (95% CI): 0.31 (0.13 - 0.70), p=0.005). The predicted probability of surgical complications based on the O1:D3 ratio indicated that osteotomy segment sizes between 0.8-0.99 (hazard ratio (95% CI): 0.23 (0.10 – 0.56) p=0.001) and 1-1.19 (hazard ratio (95% CI): 0.05 (0.01 – 0.38), p=0.004) had a lower risk of complications compared to ratios below 0.8 or above 1.2 (hazard ratio (95% CI): 0.26 (0.07 – 0.90), p=0.033).

Conclusions and clinical importance: This study highlighted the clinical importance of considering tibial tuberosity osteotomy segment size in dogs undergoing surgical treatment for MPL by retrospectively analyzing a significant number of cases, the study provided valuable insights into the incidence of postoperative complications related to osteotomy segment size. The findings indicated an association between the O1:D3 ratio (the ratio of osteotomy segment size to preselected tibial dimensions) and the occurrence of complications. Osteotomy segment sizes between 0.8-0.99 and 1-1.19 were associated with a lower risk of complications, while ratios below 0.8 or above 1.2 showed increased risk. Therefore, careful consideration of osteotomy segment size, aiming for sizes equal to or slightly larger than the mid-diaphyseal diameter, is crucial in surgical planning for dogs with MPL.